Thermionic vacuum-tube circuit



' Sept. 10, 1929.

c. SPEAKER 1,728,014

THERMIONIC VACUUM TUBE CIRCUIT Filed June '7, 1925 Charles Speaker Patented Sept. 10, 1929.

UNl'l'lEID STATES oHAnLns SPEAKER, or wasnrneron, n srnic r orco UMBIA.

THERIVIIONIC VACUUM-TUBE CIRCUIT.

Application filed. June 7,

My invention relates particularly to the control of currents and voltages in vacuum tube filament circuits supplied from an alternating current source, a *principal objectbeing to pi.'o )erly distribute potential differences in this circuit.

My invention will best be understood by references to the acconupanying jlrawiim in which the figure illustrates a radio telephone transmitting set employing vacuum tubes to generate the radio frequency carrier currents and to modulate these currents, the source of current for filament heating in these tubes beinf an alternating current. A is a microphone circuit supplying telephonic currents to a modulating circuit B containing a vacuum tube having heated filament F and C is an oscillation producing circuit having a vacuum tube containing heated filament F the modulated high frequency currents developed by the system being supplied to antenna circuit V. AC is a source of alternating; currents having a transformer T of suitable characteristics to supply heatingcurrents to the circuits of filaments F, and F The secondary S of the transformer T has a connection at its mid or neutral point M and the grid leads of the vacuum tubes are connected to this point. The filament circuits contain rheostats R, each having two resistances Pr, and R and two contactors C, and C so arranged that one resistance is in one leg of the filament circuit and one resistance in the other leg of the filament circuit, and the contactors in being rotated cut in substantially the same amount of resistance in each leg.

While it has been the general practice to provide the connection of the grid leads to a neutral point of the transformer secondary. this provision has not been entirely effective in reducing the modulation caused by the varying potential applied to the filament through using alternating; current, because it is necessary to provide a rheostat to control the value of the current in the filament circuit, and a single resistance in one leg of the filament circuit has caused an unequal distribution of filament circuit 1923. Serial no; 644,020.

potentials thereby/destroying the value of the neutral point connection.

Having described my invention I claim 1. A vacuum tube filament heating circuit having; adjustable resistances in each thereof, source of power therefor, said resistances being in series with said legs and said course of power and single means for adjusting): said resistances simultaneously and equally.

2. A vacuum tube filament heating circuit, a source of alternating current supplying said circuit, vacuum tube grid connections to the electrical neutral point of said source, and adjustable means for controlline the heating; current and equally distributing the potential differences in said circuit on bothsides of said neutral point.

3. A vacuum tube filament heating circuit, means for heating, the filament from a source of alternating current, and a single rheostat in said circuit said rheostat having a plurality of resistance elements each in seriesvrelation between a corresponding of said filament and said source of current for equally increasing" or simultaneous ly and equally decreasing the value of said resistance. a

4. In a. vacuum tube, a filamentary cathode connected to two terminals. means for energizing said filament including; separate resistances extending from each terminal and means for effecting equal magnitudes of said resistances when measured from said termin als. I

5. In combination. a vacuum tube filament circuit. means for energizing the filament from a source of alternating current, and a plurality of equally variable resistances each one of which is in series relation between a corresponding leg of said filament and said energizing means.

6. In combination. a vacuum tube filament circuit, means for energizing the filament from a source of alternating current, a plurality of equally variable resistances each one of which is in series relation between a corresponding leg of said filament and. said energizing means, means for simultaneously and equally varying the value of said resistances.

7. In combination, a vacuum tube filament circuit, means for energizing the filament from a source of alternating current, a plurality of variable resistances, each one of which isin series relation between a corresponding leg of said filament and said energizing means, and means for simultaneously and equally increasing or for simultaneously and equally decreasing the value of said resistances.

CHARLES SPEAKER. 

